In recent years, active discussions have been conducted about SON (Self Organizing Network), which autonomously optimizes a radio parameter and/or network configuration in a radio communication system such as a cellular system, in the light of operation cost (OPEX) reduction. The standardization of SON functions is also under way in 3GPP LTE (Long Term Evolution) (NPL 1).
SON has functions such as the following:
Self-Configuration;
Self-Optimization; and
Self-Healing.
These are technologies for achieving respective different purposes. Of these functions, types of self-optimization include: optimization of cell coverage and capacity (Coverage and Capacity Optimization (CCO)); optimization of a handover parameter (Mobility Robustness Optimization (MRO)); optimization of load balancing (Mobility Load Balancing (MLB)); and the like (NPL 2).
Hereinafter, the self-optimization function will be described briefly by taking a 3GPP LTE radio communication system as an example. Note that a radio base station (enhanced Node B) will be abbreviated to eNB.
As shown in FIG. 1, it is assumed that there exist macro eNBs (MeNBs) 1 and 2, which manage macro cells 1a and 2a, respectively, and a pico eNB (PeNB) 3, which manages a pico cell 3a, and that the MeNBs 1 and 2 are provided by a vendor A while the PeNB 3 is provided by a vendor B. It is further assumed that the MeNBs 1 and 2 are managed by a SON server A of the vendor A while the PeNB 3 is managed by a SON server B of the vendor B. It is each eNB, or a SON server managing it, to execute a self-optimization algorithm and determine various parameters in accordance with a purpose of the self-optimization.
For example, when the SON server A performs handover parameter optimization (MRO) for a handover between the macro cells 1 and 2, this handover parameter is determined, with consideration given to the statistics of a handover performance (e.g., handover failure rate or the number of handover failures) from the macro cell 1 to the macro cell 2 (and vice versa) or the like. Thus, the handover performance between these macro cells is improved.
On the other hand, when the SON server B performs load balancing optimization (MLB) in the pico cell 3a independently of the execution of MRO by the SON server A, the SON server B determines a parameter for a handover from the pico cell 3a to a neighbour cell, with consideration given to, for example, the loaded state of the pico cell 3a (e.g., traffic volume, hardware utilization of the PeNB) or the like. Thus, it is possible to prevent load from concentrating on the pico cell 3a, or to enhance the effects of off-loading to the pico cell 3a to improve a performance of the entire system (e.g., system throughput).
As described above, a network autonomously performs optimization, whereby it is possible to reduce the cost for an operator's manual adjustment of radio parameter and/or network parameter (OPEX).